The SPC is forecasting ...Severe thunderstorms expected over parts of the Mid South and Lower Mississippi Valley today....   Please read the latest public statement about this event.  View What is a Watch? clip.

   SPC AC 131236

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0736 AM CDT MON OCT 13 2014

   VALID 131300Z - 141200Z

   ...THERE IS A MDT RISK OF SVR TSTMS OVER PORTIONS ERN AR...NRN
   LA...NRN/WRN MS...WRN TN...SERN MO...EXTREME SRN IL...AND WRN KY...

   ...THERE IS A SLGT RISK OF SVR TSTMS ELSEWHERE FROM CENTRAL PORTIONS
   IL/INDIANA TO WRN/CENTRAL GULF COAST...TN VALLEY REGION AND WRN FL
   PANHANDLE...

   ...SUMMARY...
   STRONG TO SEVERE THUNDERSTORMS ARE EXPECTED TODAY AND TONIGHT FROM
   EAST TEXAS THROUGH THE LOWER AND MIDDLE MISSISSIPPI VALLEY TO PARTS
   OF THE TENNESSEE VALLEY...OHIO VALLEY AND GULF COAST STATES.
   WIDESPREAD DAMAGING WINDS AND A FEW TORNADOES ARE
   LIKELY...ESPECIALLY OVER THE MID SOUTH AND LOWER MISSISSIPPI VALLEY
   REGIONS TODAY.

   --- TECHNICAL DISCUSSION ---

   ...SYNOPSIS...
   HIGHLY AMPLIFIED PATTERN IS FCST THROUGH PERIOD...WITH
   PROGRESSIVE/SYNOPTIC-SCALE TROUGHS OVER NERN PAC AND MOVING EWD FROM
   CENTRAL CONUS.  PRINCIPAL SHORTWAVE TROUGH IS EVIDENT IN
   MOISTURE-CHANNEL IMAGERY OVER WRN OK AND W-CENTRAL TX.  AS THIS
   FEATURE MOVES ENEWD TODAY...500-MB CLOSED LOW SHOULD
   DEVELOP...REACHING OK/MO BORDER REGION BY 00Z WITH SHORTWAVE TROUGH
   SSWWD ACROSS MIDDLE TX COASTAL PLAIN.  BY 12Z...STRENGTHENING
   MID/UPPER LOW SHOULD REACH E-CENTRAL MO...WITH AMPLIFIED TROUGHING
   EXTENDING NWD ACROSS UPPER MS VALLEY AND SWD OVER WRN LA.

   AT SFC...COMBINED SYNOPTIC/WAKE LOW WAS ANALYZED OVER NERN OK...FCST
   TO MOVE NEWD TO WRN IL BY END OF PERIOD WHILE 500-MB CYCLONE CATCHES
   UP TO MAKE ENTIRE CYCLONIC SYSTEM MORE VERTICALLY STACKED.  STG COLD
   FRONT WILL SWEEP SEWD ACROSS OK...SWRN MO AND MOST OF CENTRAL/E TX
   BY 00Z...REACHING WRN MS...WRN TN AND WRN IL BY 12Z. 
   HOWEVER...FRONT ITSELF SHOULD BE MINOR FACTOR IN MOST OF CONVECTIVE
   SCENARIO...PERHAPS OVERTAKING SRN PARTS OF QLCS SOONEST.

   ...MID-SOUTH TO GULF COAST AND OH VALLEY...
   REF WWS 532-534 AND ACCOMPANYING MESOSCALE DISCUSSIONS FOR NEAR-TERM
   THREAT AREAS. 

   DAMAGING WINDS WILL BE PRIMARY THREAT FROM SVR TSTMS SWEEPING EWD
   OVER THIS CORRIDOR TODAY...THOUGH SPORADIC...MARGINALLY SVR HAIL
   ALSO MAY OCCUR.  A FEW TORNADOES ALSO ARE POSSIBLE...WHETHER FROM
   MAIN QLCS OR FROM FOREGOING SUPERCELLS IN VERY MOIST...WEAKLY CAPPED
   WARM SECTOR TODAY AND TONIGHT.

   WELL-ORGANIZED QLCS...WITH HISTORY OF EFFECTIVELY JUMPING EWD TO
   POSITION OF YOUNGER/INTENSIFYING WARM-SECTOR TSTM BANDS...CONTINUES
   TO EXHIBIT THAT BEHAVIOR ATTM OVER E TX.  RESULTING BAND OF STG-SVR
   TSTMS IS FCST TO PROCEED EWD ACROSS OUTLOOK AREA WITH INCREASING SVR
   RISK THROUGH AFTN...WHILE NRN END STRENGTHENS INVOF OZARKS AND
   ACCELERATES NEWD TOWARD LOWER OH VALLEY.  TRANSLATION OF THIS
   CONVECTION ALREADY IS FASTER THAN ALL KINDS OF MODELS HAVE
   INDICATED...EVEN SHORT-FUSED/RADAR-ASSIMILATING GUIDANCE LIKE HRRR
   THAT SHOULD PERFORM BEST AT KEEPING UP WITH SUCH TENDENCIES.  THIS
   SITUATION MAY PERSIST THROUGH MOST OF TODAY DESPITE SOME GUIDANCE
   SHOWING DECELERATION OF QLCS E OF MS RIVER.  AS SUCH...OUTLOOK LINES
   HAVE BEEN SHIFTED/TRIMMED EWD IN DEFERENCE TO RECENT AND PROJECTED
   TRENDS.

   FOREGOING AIR MASS...THOUGH MOSTLY CLOUDY FROM AR AND MS
   NWD...SHOULD DESTABILIZE FROM COMBINATION OF WARM/MOIST ADVECTION
   AND POCKETS OF SFC DIABATIC HEATING.  RESULTING BOUNDARY-LAYER
   THETAE INCREASE WILL OFFSET MODEST MIDLEVEL LAPSE RATES ENOUGH TO
   BOOST PRECONVECTIVE/AFTN MLCAPE TO 1500-2000 J/KG OVER PORTIONS
   MID-SOUTH AND LOWER MS VALLEY...DIMINISHING NWD THROUGH IL. 
   MEANWHILE VERTICAL SHEAR WILL INCREASE WITH TIME PRIOR TO QLCS
   ARRIVAL...EXCEPT PERHAPS OVER PARTS OF S-CENTRAL/SE TX WHERE MORE
   MODEST INCREASE IN FLOW ALOFT MAY BE OFFSET IN SHEAR CALCULATIONS BY
   VEERING SFC WINDS.

   AS MID-UPPER TROUGH AMPLIFIES...FOREGOING WINDS ALOFT WILL BACK TO
   BECOME MORE MERIDIONAL...REDUCING BOTH
   1. DEEP-LAYER DIRECTIONAL SHEAR AND
   2. ALREADY SMALL COMPONENT OF WINDS ALOFT THAT ARE ORTHOGONAL TO
   BAND OF CONVECTIVE FORCING.
   IN FACT...FCST SOUNDINGS NEAR AND E OF MS RIVER...JUST AHEAD OF MAIN
   CONVECTIVE BAND...SHOW SOME BACKING OF WIND WITH HEIGHT IN VARIOUS
   PARTS OF 700-500-MB LAYER.  THESE FACTORS FORETELL LIKELY
   MAINTENANCE OF DOMINANT QUASILINEAR MODE.  EMBEDDED LEWP/BOW
   FEATURES STILL MAY DEVELOP CIRCULATIONS CAPABLE OF LOCALLY ENHANCED
   WIND-DAMAGE SWATHS AND SMALL/BRIEF TORNADOES.  MEANWHILE...A FEW
   SUPERCELLS MAY DEVELOP AHEAD OF PRIMARY QLCS...ESPECIALLY FROM
   MID-SOUTH REGION THIS AFTN TO PORTIONS MS/AL THIS EVENING AND
   OVERNIGHT...IN REGIME OF RICH MOISTURE...LOW LCLS AND FAVORABLE
   HODOGRAPHS.  AS SUCH...CATEGORICAL-THRESHOLD TORNADO PROBABILITIES
   HAVE BEEN EXPANDED SEWD ACROSS MS/AL...WHILE BEING TRIMMED ON WRN
   EDGE AS NOTED ABOVE DUE TO CONVECTIVE TRENDS.

   SVR-THREAT AREA MAY EFFECTIVELY PINCH OFF FROM NW-SE DURING
   MIDDLE-LATTER PARTS OF PERIOD AS MAIN CONVECTIVE REGIME OUTRUNS MOST
   FAVORABLE DESTABILIZATION.  HOWEVER...SVR THREAT SHOULD PERSIST
   THROUGH TONIGHT ACROSS DIXIE PORTION OF OUTLOOK.

   ..EDWARDS/MOSIER.. 10/13/2014

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   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 1630Z